def f(*x):
    if len(x) == 0:
        return 0
    j = 1
    for i in range(len(x)):
        j *= x[i]
    return j


if __name__ == "__main__":
    r1 = f(10, 20, 30)
    print(r1)
    r3 = f(10)
    print(r3)
    r4 = f()
    print(r4)
